Electric Motor Boat

Electric boat in action.

Today, we turned a toy aeroplane that did not work very well into a cool motor boat. Well, we didn't turn the aeroplane into a boat, but we did use the motor and the propeller from the plane.

The aeroplane we used was supposed to be suspended from the ceiling from a bit of string and switched on. The propeller at the back pushed the plane forward and it was supposed to go around in circles. The only problem was that it didn't. The plane was too heavy and the propeller was too small, so it never really worked.

I used a screwdriver to carefully remove the four screws that held the plane together. Once the screws were out, the motor and the propeller came out quite easily, and we put the whole plane together again so we can still play with it.

Wire insulation as a shaft coupling.

Next we tested the motor and the switch. All was in working order, but there were two problems. We got the wires the wrong way around, which means our boat would have gone backwards, but that one was easy to fix. The second problem was that the motor shaft and the propeller shaft were linked by a short bit of plastic tubing. The tube was a little too short, and kept on slipping off the shafts, so we needed a new bit of tubing. We found that the insulation on an extension lead was exactly the right size, and made a nice snug fit.

Prestik holding motor and batteries.

Next we took a polystyrene food tray and made a small hole for the propeller shaft. We needed the motor to be at an angle, and a large blob of prestik did a very good job. The prestik also held the battery pack and the switch in place.

We cut a rudder from a bit of aluminum pie plate, and wrapped it around a tooth pick. We set this off to one side so that it would not foul the propeller and we were ready for a test run.

Wine cork buoy.

The boat performed beautifully and zoomed across the swimming pool. Euan made some buoys out of corks. He put a screw into the bottom of half a wine bottle cork and a tooth pick into the top. To finish it off he put an aluminum flag on top of the tooth pick. The buoys were ready and worked really well.

The final bit of fun was trying to set the rudder so that the boat zoomed between the buoys.

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General layout.

Propeller and rudder.

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All of the pictures are here.

Fruit and Veg Batteries

This week we decided to see if we could get electricity out of fruit and veg. We used: a voltmeter a tomato a lemon a bit of play dough an old battery

First we carefully cut open an old zinc-carbon cell and peeled off a few strips of the zinc casing.  Then we used the back of a knife to scrape the zinc strip until it was clean and shiny.

We touched the two probes of the voltmeter together and the meter showed zero.  Then we stuck a piece of copper wire into one side of the bit of play dough and the zinc strip into the other side of the play dough, and then measured the voltage. Still zero!

Next we tried a tomato.  With the zinc strip in one side of a small tomato, and the copper wire in the other side, the voltage between the electrodes was 0.78 volts.  After the tomato, we tried a lemon.  This gave us 0.85 volts.

The last thing we tried was to make a battery by connecting a tomato and a lemon in series.  We took a strip of zinc and folded it around a bit of copper wire.  The zinc side went into the lemon and the copper wire into the tomato.  Another bit of wire went into the lemon and a second strip of zinc went into the tomato.  This gave us a voltage of 1.7 volts!

Next time we will try to light up an LED.

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View all the pictures on here.

Keeping Air - Getting a good seal

We decide to see how well a normal party balloon can keep air. First we blew up some balloons and then slipped them over the top of some glass bottles. After 4 weeks, 4 of the ballons are still up. Some lost all of their air but four of them kept about half their air. This means that the seal between the glass bottle and the balloon is very good.

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